Please refer to FIG. 1 and FIG. 2, which show an electrochemical sensor strip 10 disclosed in patent application TW 1294964. The electrochemical sensor strip 10 has an insulation substrate 12 having a reaction recess 11, an electrochemical reactive layer 13 in the reaction recess 11, a cover portion 14, an opening 15, two through holes 16 formed at the bottom of the reaction recess 11 and two electrodes 17 respectively placed in the through holes 16 and contact with the electrochemical reactive layer 13. The two electrodes 17 are a counter electrode and a working electrode.
The electrochemical sensor strip 10 is used to detect an analyte in a sample fluid 18. There is an electrochemical reaction performed between the analyte and the electrochemical reactive layer 13, and a signal current is generated for the electrodes 17 to detect after the sample fluid 18 enters and fully fills the reaction recess 11 via the opening 15.
The size of the reaction recess 11 is about 6 mm length, about 1.2 mm width and about 0.8 mm height. The volume is therefore approximately 0.6 mm3. At least approximately 0.6 μL, of the sample fluid 18 is required to fully fill the reaction channel.
Although the complete electrochemical reactive layer 13 without being eroded by an erosion process can be used in the electrochemical sensor strip 10 to improve the accuracy of the electrochemical reaction, it still requires the configuration of two electrodes 17 which raises the usage of noble metals (such as a gold, a platinum, a palladium, or a rhodium), and therefore there is a failure to reduce the cost. Further, the reaction recess 11 must have a certain area to configure the two through holes 16 at the bottom. Accordingly, it is still difficult to reduce the volume of the sample fluid 18 to fully fill the bottom area of the reaction recess 11, which does not meet the goal of reducing the required sample fluid 18.
Please refer to FIG. 3, which is an electrochemical sensor strip 90 disclosed in patent application TW 1254795 (or U.S. Pat. No. 7,740,746). The electrochemical sensor strip 90 has a lower insulation piece 91, a fluid measurement recess 92 formed on the lower insulation piece 91, a through hole 93 connected to the fluid measurement recess 92, a first electrode 94 placed in the through hole 93, a conductive track 95 coupled to the first electrode 94, a upper insulation piece 96, a second conductive track 97 and a third conductive track 98 respectively printed on the upper insulation piece 96. Although the design of the upside and downside configuration of the electrodes can reduce the difficulty of printing, there are still the steps of multi-printing the conductive track in the strip manufacturing process. There is still room to raise the process efficiency. Accordingly, a strip which can eliminate printing the conductive track and reduce the required volume of the sample fluid at the same time is a worthwhile goal that deserves further research in this field.
In order to overcome the drawbacks in the prior art, a biosensor strip is disclosed. The particular design in the present invention not only solves the problems described above, but is also easy to implement. Thus, the present invention has utility for the industry.